The present invention relates generally to a method and apparatus for forming a layer of blown cellular polyurethane on a textile material, such as a carpet backing. More specifically, the present invention relates to a method and apparatus for providing improved control of properties, such as bond, gauge control and foam density, for blown cellular polyurethane products.
U.S. Pat. Nos. 4,132,817; 4,171,395; 4,405,393; 4,512,831; 4,715,912 (the disclosures of which are all incorporated herein by reference) disclose apparatus and processes by which a layer of blown cellular polyurethane; i.e., polyurethane foam, can be formed on a textile material, such as a fabric or carpet back. This process has been used commercially for many years. In the system disclosed in the above-referenced patents, when a relatively heavy blanket weight is applied to the expanding polyurethane reactants, the density of the foam increases and gauge; i.e., foam thickness, is difficult to control. With no blanket weight, the foam and fabric bond is inhibited due to inconsistent contact between the fabric and foam, while at the same time creating a gauge control problem. Furthermore, changes in line speed; i.e., conveyor belt speed, can also influence bond and gauge control. If the conveyor belt speed is reduced, the marriage of the fabric to the reacting foam is slowed and the bond between the two will be relatively weak and inconsistent, or not bonded at all in extreme circumstances. On the other hand, if line speed is increased the foam reaction is effectively slowed down allowing the fabric to marry into the wet chemical mixture, which can result in distortion of the gauge, as well as bleed-through of the chemical into the fabric and incomplete curing of the foam.
Thus, there is a need in the art for a system that provides improved control of the properties of foam-to-fabric bond, gauge and foam density.
The present invention relates to a method for forming a layer of blown cellular polyurethane on a textile material, such as a carpet backing. The method includes applying to a textile material a layer of reactive polyurethane forming agents containing a sufficient amount of heat-sensitive blowing agent so as to cause chemical blowing of the mixture when heated sufficiently, heating the layer so as to cause chemical blowing of the mixture and applying to the layer during the chemical blowing thereof a pressure of an amount and for a time sufficient to control the blowing of the mixture to a desired degree, the pressure being applied to the mixture continuously from an initial pressure to a final pressure, wherein said initial pressure is greater than the final pressure.
In another embodiment, there is an apparatus for forming a layer of blown cellular polyurethane on textile material. The apparatus comprises a continuous conveyor belt upon which a quantity of reactive polyurethane forming agents can be deposited, a mixer for mixing reactive polyurethane forming agents and depositing them on the conveyor belt, a means for applying a textile material to the polyurethane forming agents deposited on the belt, a means for heating the polyurethane forming agents deposited on the belt, and a means for applying a plurality of different pressures to the textile material and polyurethane forming agents deposited on the belt during the chemical blowing thereof.
Accordingly, it is an object of the present invention to provide an improved method and apparatus for forming a layer of blown cellular polyurethane on a textile material; particularly, a carpet back.
Another object of the present invention is to provide an improved method and apparatus that can apply a plurality of different pressures to a layer of reactive polyurethane forming agents during the chemical blowing thereof.
These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments and the appended drawing and claims.